Conventional vehicle door lock apparatuses are disclosed in Patent Literatures 1 and 2. These vehicle door lock apparatuses include a housing provided in a door for opening and closing an opening of a vehicle body and including an entry opening that a striker fixed to the vehicle body enters, a fork pivotably provided in the housing and switched to a latched state for locking the striker in the entry opening or an unlatched state for unlocking the striker in the entry opening, and a pawl pivotably provided in the housing and capable of fixing or releasing the pivoting movement of the fork.
The vehicle door lock apparatus disclosed in Patent Literature 1 includes a first lever pivotably provided in the housing and one end side of which is coupled to a door handle, a second lever pivotably supported, on the other end side of the first lever, around a pivot extending in a direction orthogonal to a direction of advancing to and retracting from the opening, and a biasing member provided between the housing and the second lever. In FIG. 1 and the like of Patent Literature 1, the first lever is shown as reference numeral 14, the second lever is shown as reference numeral 48, and the biasing member is shown as reference numeral 52. The first lever pivots by an opening operation of the door handle. The second lever is pivotable from a first position to a second position by application of inertial force at the time of, for example, a vehicle collision. The biasing member biases the second lever toward the first position.
In this vehicle door lock apparatus, when the first lever pivots, the second lever which is usually disposed in the first position comes into contact with the pawl and release the pivoting movement of the fork, so that the fork in the latched state is switched to the unlatched state. On the other hand, at the time of, for example, the vehicle collision, the second lever is displaced to the second position while resisting a biasing force of the biasing member and separates from the pawl; therefore, even if the first lever pivots, the fork in the latched state is not switched to the unlatched state. In this way, the vehicle door lock apparatus disclosed in Patent Literature 1 attains prevention of an unintended opening of the door at the time of, for example, the vehicle collision.
On the other hand, the vehicle door lock apparatus disclosed in Patent Literature 2 includes an open member coupled to a door handle and displaced by the opening operation of the door handle, a linking member displaced to come into contact with a pawl and release pivoting movement of a fork, a transmitting member coupled to a locking knob and, in the case in which the locking knob is in an unlocked state, displaced to a transmittable position for transmitting the displacement of the open member to the linking member and, on the other hand, in the case in which the locking knob is in a locked state, displaced to an un-transmittable position where the displacement of the open member is not transmitted to the linking member, and a motion accumulating mechanism interposed between the transmitting member and the locking knob.
As shown in FIG. 2 and the like of Patent Literature 2, the motion accumulating mechanism is configured to, in the case in which an unlocking operation of the locking knob and the opening operation of the door handle overlap, when the displacement of the transmitting member is prevented while the transmitting member is displaced from the un-transmittable position to the transmittable position, accumulate motions of the locking knob thereafter and, when the displacement of the transmitting member is not prevented, displace the transmitting member to the transmittable position. In this way, even when the unlocking operation and the opening operation of the door overlap, the vehicle door lock apparatus disclosed in Patent Literature 2 eliminates the need to perform the unlocking operation of the locking knob again.